Preparation of 5-benzylhydantoin



Patented Aug. '16, 1949 u mrszo STATES I anacea v f ,7

PREPARATION F S-BENHIiHYDAN-TOIN William F. 'Gres'hamfWilniington, ner,-assigns to E. I. flu Pont de Nemours -& Company,"Wil 'niingtom'DeL, a "corporation of Delaware Nollrawing. Application Sep ember v SerialNo.

This invention :relates to the preparation of 5-benzylhydantoin and in particular 'to 'anovel method for hydrogenating 5-benzalhydantoin to 5-benzylhyd'an'toin.

Heretofore 5-benzylhydantoin has been prepared Joy reduction of 5-ben-"za1hy'cl'antoin through the .use of warious reducing agents such as hydrogen iodide-red phosphorus, ammonium sulficle, sodium hydrogen sulfide, hydrogen sulfide and the like (-Biocihem. J.', "2'9, 546). Evidently, these specific reducing agents were considered to be necessary in view of it-he peculiar structure of 5-benzalhydaritoin. Thus,f'or example, it was not feasible to employ catalytic hydrogenation processes which would hydrogenate the aromatic nucleus, since a selective reduction of the ethylenic linkage of fi-benzalhydantoin was desired.

An object of this invention is to provide an improved and practical method for the preparation of 5-benzylhydantoin. A further object is to provide a process for catalytic hydrogenation of 5- benzalhydantoin to 5-benzylhydantoin. A still further object is to obtain 5-benzylhydantoin from 5-benzalhydantoin in virtually theoretical yields.

It has been discovered, in accordance with the invention that 5-benzylhydantoin can be obtained in excellent yield by hydrogenating 5- benzalhydantoin under sufficiently mild conditions, to prevent hydrogenation of the aromatic nucleus of these compounds. The hydrogenation of 5-benzalhydantoin to fi-benzylhydantoin is accomplished in accordance with the invention in the presence of a hydrogenation catalyst at temperatures within the range of about 40 to 150 (3., preferably about to 100 C. Whena nickel alloy type catalyst is employed at temperatures below about 85 C., the yield of 5- benzylhydantoin is nearly quantitative. In a specific embodiment, s-benzalhydantoin is hydrogenated in the presence of a nickel-aluminum alloy catalyst at a temperature of about to C. under a pressure of about 200 to 1000 atmospheres; a rapid hydrogenation rate is obtained, and yields of 5-benzylhydantoin are within the range of about 97 to 100%. The reaction which takes place in accordance with the invention may be written as follows:

5 Claims. (Q1. ZED-"3093) Theinventicn i-sf iuustrated further by means ofithe 'f'ollowingexanrples'.

Example "1 mixture containing 1551 "grams of. 5 menial-hydantoin, '20 grams of caustic-activated nickel-almnmulmalloy catalyst and 200 cc. of methanol was heated for one hour at 'a temperature o'f iill "to-93 -13.twithhydrogen under a pressure -of 755 'toi76'0'atmospheres; The resulting product fwa'sffillflzl'fi'fl *wliile warm, and the filtrate was evaporated comm rIin 'tliismanner, a residue "(131 grams) 'ihaving melting point of 1-8? "to C. was :fibtained. This corre- 'spondstoan 85i'9'% "yilfi of' 'b -benzylhydantoin.

Example 2.-'-A*niixtm'e *contaiii-ing 14.1 'grams of 5-benzalhydantoin dissolved in 200 cc. of

- methanol was heated in the presence of 20 grams are illustrative only and should not be construed as limiting the invention in any way. Any suitable reaction medium, such as an inert organic solvent, or non-solvent may be used, if desired,

Hydrogenation catalysts other than nickel alloy catalysts, including, for example, platinum, finely divided nickel, supported nickel, and cobalt, are generally effective, but the activated nickelaluminum alloy catalysts are preferred. Best results are obtained at superatmospheric pressure, but it'is not essential to employ pressures as high as those illustrated in the examples, unless a rapid reaction rate is desired. Generally speaking, optimum results are obtained at pressures of from 50 to 1500 atmospheres, preferably about 200 to 1,000 atmospheres,

The 5-benzylhydantoin prepared in accordance with this invention is of excellent quality. It is useful as an intermediate in the manufacture of the essential amino acid, phenylalanine,

' which may be prepared therefrom by methods known to the art.

I claim:

1. A process for the preparation of 5-benzylhydantoin from 5-benzalhydantoin and hydrogen without hydrogenation of the aromatic nucleus which is present in the said hydantoin compounds, which comprises reacting 5-benzalhydantoin with hydrogen in the presence of a caustic-activated nickel-aluminum alloy catalyst at a temperature of about 50 to 100 C. under a pressure of about 50 to 1500 atmospheres, and thereafter separating 5-benzylhydantoin from the resultant hydrogenation product.

2. A process for the preparation of 5-benzy1- hydantoin from 5-benzalhydantoin and hydrogen without hydrogenation of the aromatic nucleus which is present in the said hydantoin compounds, which comprises reacting 5-benzalhydantoin with hydrogen in the presence of an inert organic solvent and a, caustic-activated nickel-aluminum alloy catalyst at a temperature of about 50 to 100 C. under' a pressure of about 50 to 1500 atmospheres, and thereafter separating 5-bcnzylhydantoin from the resultant hydrogenation product.

3. A process for the preparation of 5-benzylhydantoin from S-benzalhydantoin and hydrogen without hydrogenation of the aromatic nucleus which is present in the said hydantoin compounds, which comprises reacting 5-benza1- hydantoin with hydrogen in the presence of methanol and a caustic-activated nickel-aluminum alloy catalyst at a temperature of about 50 to 100 C. under a pressure of about 50 to 1500 atmospheres, and thereafter evaporating methanol from the liquid reaction product whereby a residue of 5-benzy1hydantoin is obtained.

4. A process for the preparation of 5-benzy1- hydantoin from 5-benza1hydantoin and hydrogen without hydrogenation of the aromatic nucleus which is present inthesaid hydantoin compounds, which comprises reacting 5-benzalhydantoin with hydrogen-in the presence of an inert organic reaction medium and a causticactivated nickel-aluminum alloy catalyst at a temperature of 80 to 85 C. under a pressure of comprises heating a methanol solution of about 14.1 parts by weight 5-benza1hydantoin with about 20 parts by weight of caustic-activated nickel-aluminum alloy catalyst for about one hour at a temperature of about 80 to C., under apressure in the range of about 725 to 730 atmospheres for about one hour, whereby 5-benzylhydantoin is formed in high yield.

WILLIAM F. GRESHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,263,796 Nomura Apr. 23, 1918 2,381,210 Cotton Aug. 7, 1945 OTHER REFERENCES Adkins: Reactions of Hydrogen (1946),

University of Wisconsin Press, Madison, Wisconsin, pp. 129, 147 and 148.

Biochemical Journal, vol. 29, p. 546. 

